Definition
Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite).
Chalk is a soft, white, powdery limestone consisting mainly of fossil shells of foraminifers
History
Origin
Brazil
-
Discoverer
Unknown
Unknown
Etymology
from French néphéline, from Greek nephelē
From old English cealc chalk, lime, plaster; pebble, from Greek khalix small pebble, in English transferred to the opaque, white, soft limestone
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Soft Rock
Family
Group
Plutonic
-
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Aphanitic
Clastic or Non-Clastic
Color
Black, Brown, Green, Grey, White
Grey, White, Yellow
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
✔
✘
✔
✘
Scratch Resistant
✔
✘
✔
✘
Stain Resistant
✔
✘
✔
✘
Wind Resistant
✔
✘
✔
✘
Acid Resistant
✔
✘
✔
✘
Appearance
Skeletal
Soft
Architecture
Interior Uses
Decorative Aggregates, Homes, Interior Decoration
Decorative Aggregates, Homes, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration
Other Architectural Uses
Curbing
Powder
Industry
Construction Industry
As Dimension Stone, Cement Manufacture, Construction Aggregate, for Road Aggregate
As Dimension Stone, Cement Manufacture, Construction Aggregate, for Road Aggregate, Making natural cement, raw material for manufacture of quicklime and slaked lime, Source of calcium
Medical Industry
-
-
Antiquity Uses
Artifacts, Monuments, Sculpture, Small Figurines
Artifacts, Monuments, Sculpture, Small Figurines
Other Uses
Commercial Uses
Creating Artwork, Soil Conditioner, Source of Magnesia (MgO)
Alumina Refineries, Creating Artwork, Drawing on blackboards, Gymnasts, athletes and mountain climbers use for grip, In aquifers, Paper Industry, Production of Lime, Raw material for manufacture of quicklime, slaked lime, Soil Conditioner, Whiting, Whiting material in toothpaste, paint and paper
Types
Peralkaline Nephelinite
Chalk Marl and Marl
Features
Host Rock for Lead
Clasts are smooth to touch, Is one of the oldest rock, Smooth to touch, Very fine grained rock
Archaeological Significance
Monuments
-
-
Famous Monuments
-
-
Sculpture
-
-
Famous Sculptures
-
-
Pictographs
-
-
Petroglyphs
-
-
Figurines
-
-
Fossils
Absent
Present
Formation
Nephelinite is a fine-grained, hard rock which is a type of metasomatite, essentially altered basalt. It forms with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
Chalk is formed from lime mud, which accumulates on the sea floor which is then transformed into rock by geological processes.
Composition
Mineral Content
Clinopyroxene, Nepheline, Plagioclase
Calcite, Clay, Clay Minerals, Quartz, Sand
Compound Content
Ca, CaO, Carbon, Cl, MgO
Ca, NaCl, CaO
Transformation
Metamorphism
✔
✘
✔
✘
Types of Metamorphism
Contact Metamorphism
-
Weathering
✔
✘
✔
✘
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering
Erosion
✔
✘
✔
✘
Types of Erosion
Chemical Erosion, Water Erosion, Wind Erosion
Chemical Erosion, Coastal Erosion, Water Erosion
Physical Properties
Hardness
6.51
1
7
👆🏻
Grain Size
Fine Grained
Very fine-grained
Fracture
Flat
-
Streak
White
White
Porosity
Less Porous
Highly Porous
Luster
Vitreous to Metallic
Dull
Compressive Strength
35.00 N/mm25.00 N/mm2
0.15
450
👆🏻
Cleavage
-
-
Toughness
2.7
1
Specific Gravity
2.4-2.92.3-2.4
0
8.4
👆🏻
Transparency
Opaque
Opaque
Density
2.5-3 g/cm32.49-2.50 g/cm3
0
1400
👆🏻
Thermal Properties
Specific Heat Capacity
0.88 kJ/Kg K0.90 kJ/Kg K
0.14
3.2
👆🏻
Resistance
Heat Resistant
Heat Resistant
Deposits in Eastern Continents
Asia
Japan
Brunei, India, Indonesia, Malaysia, Singapore, Thailand, Vietnam
Africa
Rwanda, Tanzania
Cameroon, Chad, Ghana, Kenya, Malawi, Sudan, Tanzania, Togo, Zambia, Zimbabwe
Europe
-
England, France, Germany, Spain, United Kingdom
Others
Hawaii Islands
-
Deposits in Western Continents
North America
Canada, USA
Canada, USA
South America
Colombia
Colombia
Deposits in Oceania Continent
Australia
-
Adelaide, New Zealand, Queensland, Victoria, Yorke Peninsula